There is a need for a hearing aid to improve the audibility of sound, etc., in response to distinguishing between sound and non-sound and the degree of surrounding noise, undesired sound, or reverberation and play high-clarity sound independently of the sound environment. To meet the need, there is a hearing aid including a hearing aid main body to which a volume change button and an operation mode change button are added for enabling a person wearing the hearing aid to consciously change setting in response to the use scene and the sound environment (for example, see Patent Document 1).
On the other hand, as a technique for the hearing aid user to unconsciously change setting in response to the sound environment, there is a signal processing technique of classifying various acoustic signals previously (learning phase) and automatically changing setting of amplification, etc., of an input acoustic signal in response to the sound environment using the acoustic signals classified in the learning phase (for example, see Patent Document 2).
As a method of changing setting through another device other than the hearing aid main body, as for adjustment of an acoustic parameter, there is a technique in which a mobile device is connected to a server and a hearing chart database through a network and which can adjust the sound quality of the mobile device (for example, see Patent Document 3).
Further, there is a technique in which a telephone generates a control signal of a hearing aid and converts the control signal together with a receiving signal into a sound wave and transmits the sound wave. FIG. 12 is a block diagram to show a configuration example of such a remote control hearing aid system. This remote control hearing aid system includes a telephone 10 and a hearing aid 40.
When a telephone call starts, a call detection unit 6 of the telephone 10 detects the call. When the call detection unit 6 detects the call, a control signal generation unit 5 generates a control signal. The control signal and a receiving signal are converted into an acoustic signal by an electroacoustic transducer 4 and the acoustic signal is transmitted to the hearing aid 40.
The transmitted acoustic signal is received by a sound wave reception unit 41 of the hearing aid 40 and is converted into reception signal of an electric signal. The reception signal provided by the sound wave reception unit 41 is sent through a reception switch unit 43 to a power amplification unit 44 and an analysis control unit 46. The sent reception signal is subjected to frequency analysis and is compared with a stored signal in the analysis control unit 46, whereby a control signal is generated. The control signal is sent to the power amplification unit 44 and is used to change the amplification factor of the reception signal (for example, see Patent Document 4).